Beam steering method and device

ABSTRACT

A beam steering method and device are provided. The beam steering method includes outputting, from a hologram recording medium on which a plurality of signal light beams having different steering information are recorded, signal light beam having specific steering information, by making reference light having a specific characteristic incident on the hologram recording medium. The method further includes o obtaining information about an object existing in the external environment based on the output signal light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2018-0053204, filed on May 9, 2018, in the Korean IntellectualProperty Office, and U.S. Patent Application No. 62/552,004, filed onAug. 30, 2017, in the U.S. Patent and Trademark Office, the disclosuresof which are incorporated herein in their entirety by reference.

BACKGROUND 1. Field

Apparatuses and methods consistent with exemplary embodiments relate tobeam steering methods and devices.

2. Description of the Related Art

There is a growing interest in techniques for measuring distances ordirections to objects, identifying objects, terrain, etc., and fordetecting the speed, temperature, and material distribution of an objectusing light. In this regard, studies have been conducted on methods ofsteering the direction of emitted light.

To steer light in a desired direction, a method of mechanically rotatinga light source has been used, as well as a method in which a bundle-typebeam emitted from a plurality of unit cells or a plurality of waveguidesis steered using an optical phased array (OPA). The method ofmechanically rotating the light source uses a motor or a micro electromechanical system (MEMS), which may increase the volume and cost of adevice. The OPA method may steer the beam by electrically or thermallycontrolling unit cells or waveguides. In the OPA method, a plurality ofwaveguides are required, which may increase the total volume of a deviceand cause an error in phase modulation.

SUMMARY

One or more exemplary embodiments may provide beam steering deviceshaving simple structures and beam steering methods.

One or more exemplary embodiments may provide beam steering devicesusing a beam recorded via a hologram method and beam steering methods.

Additional exemplary aspects and advantages will be set forth in part inthe description which follows and, in part, will be apparent from thedescription, or may be learned by practice of the presented exemplaryembodiments.

According to some exemplary embodiments, a beam steering method includesmaking reference light incident on a hologram recording medium on whicha plurality of signal light beams, having different steeringinformation, are recorded in a holographic manner; outputting, to anexternal environment, a signal light beam having specific steeringinformation that reacts with a characteristic of the reference light,from among the plurality of signal light beams; and obtaininginformation about an object existing in the external environment usingthe output signal light.

The outputting of the signal light may include outputting a first signallight beam having first steering information that reacts with a firstreference light beam having a first characteristic; and outputting asecond signal light beam having second steering information that isdifferent from the first steering information and reacts with a secondreference light beam having a second characteristic different from thefirst characteristic.

The characteristic may include at least one of a wavelength and a phaseof light.

The specific steering information may include at least one of an outputdirection and a divergence angle of the signal light beam.

Information about the object may include at least one of absence orpresence of the object, a position of the object, and distanceinformation about the object.

The outputting of the signal light may include outputting a first signallight group comprising a plurality of signal light beams havingdivergence angles greater than a reference angle; and outputting asecond signal light group comprising a plurality of signal light beamshaving divergence angles less than the reference angle.

The outputting of the first signal light group may include scanning theexternal environment by outputting the plurality of signal light beamsincluded in the first signal light group in different output directions.

The outputting of the first signal light group may include sequentiallyoutputting one by one the plurality of signal light beams included inthe first signal light group.

The obtaining of the information about the object may includedetermining a target region in which the object exists in the externalenvironment based on the first signal light group.

The outputting of the second signal light group may include scanning thetarget region by outputting the plurality of signal light beams includedin the second signal light group in different output directions.

The obtaining of the information about the object may include obtainingdistance information about the object based on the second signal lightgroup.

According to some exemplary embodiments, a beam steering device includesa light source configured to output a plurality of reference light beamshaving different characteristics; and a hologram recording medium onwhich a plurality of signal light beams having different steeringinformation are recorded in a holographic manner and configured to scanan external environment by outputting the plurality of signal lightbeams having different steering information that reacts with acharacteristic of each of the plurality of reference light beamsincident thereon from the light source.

The hologram recording medium may be configured to output a first signallight beam having first steering information that reacts with a firstreference light beam having a first characteristic and to output asecond signal light beam having second steering information that isdifferent from the first steering information and reacts with a secondreference light beam having a second characteristic different from thefirst characteristic.

The characteristic may include at least one of a wavelength and a phaseof light.

The steering information may include at least one of an output directionand a divergence angle of the signal light beam.

The beam steering device may further include: a processor configured toobtain information about the object existing in the external environmentbased on the output plurality of signal light beams.

The information about the object may include at least one of absence orpresence of the object, a position of the object, and distanceinformation about the object.

The hologram recording medium may be configured to output at least oneof a first signal light group comprising a plurality of signal lightbeams having divergence angles greater than a reference angle and asecond signal light group comprising a plurality of signal light beamshaving divergence angles less than the reference angle.

The hologram recording medium may be configured to output the pluralityof signal light beams included in the first signal light group indifferent output directions.

The processor may be configured to determine a target region in whichthe object exists in the external environment using the first signallight group and to obtain distance information about the object based onthe second signal light group.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other exemplary aspects and advantages will become apparentand more readily appreciated from the following description of theexemplary embodiments, taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a block diagram showing a beam steering device according to anexemplary embodiment;

FIGS. 2A and 2B are reference diagrams for explaining wide range signallight according to an exemplary embodiment;

FIG. 3 is a reference diagram for explaining a method of scanning theexternal environment by using wide range signal light according to anexemplary embodiment;

FIGS. 4A and 4B are reference drawings for explaining narrow rangesignal light according to an exemplary embodiment;

FIG. 5 is a reference diagram for explaining a method of scanning theexternal environment by using a plurality of narrow range signal lightbeams according to an exemplary embodiment;

FIG. 6A is a diagram for explaining a relationship between referencelight and signal light according to an exemplary embodiment;

FIG. 6B is a diagram illustrating an example in which signal light scansthe external environment according to an exemplary embodiment;

FIG. 7 is a flowchart for explaining a method of scanning the externalenvironment using signal light according to another exemplaryembodiment; and

FIGS. 8A and 8B are diagrams showing a scanning device including aplurality of hologram recording media.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments which areillustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentexemplary embodiments may have different forms and should not beconstrued as being limited to the descriptions set forth herein.Accordingly, the exemplary embodiments are merely described below, byreferring to the figures, to explain aspects. Most of the terms usedherein are general terms that have been widely used in the technical artto which the present disclosure pertains. However, some of the termsused herein may be created reflecting intentions of technicians in thisart, precedents, or new technologies. Also, some of the terms usedherein may be arbitrarily chosen by the present applicant. In this case,these terms are defined in detail below. Accordingly, the specific termsused herein should be understood based on the unique meanings thereofand the whole context of the present disclosure.

In the present specification, it should be understood that the terms,such as ‘including’ or ‘having,’ etc., are intended to indicate theexistence of the features, numbers, steps, actions, components, parts,or combinations thereof disclosed in the specification, and are notintended to preclude the possibility that one or more other features,numbers, steps, actions, components, parts, or combinations thereof mayexist or may be added.

It will be understood that what is described as ‘upper’ or an ‘on’ mayinclude not only being directly on, but also being in a noncontactmanner. It will be understood that although the terms “first”, “second”,etc. may be used herein to describe any of various elements, theseelements should not be limited by these terms. These terms are only usedto distinguish one element from another.

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Thefollowing exemplary embodiments are intended to illustrate thedisclosure and do not limit or restrict the scope of the disclosure. Itwill be understood by those of ordinary skill in the art that variouschanges in form and details may be made therein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims.

FIG. 1 is a block diagram showing a beam steering device according to anexemplary embodiment. Referring to FIG. 1, a beam steering device 10 mayinclude a scanning device 120 which scans the external environment usinglight and a processing device 140 which obtains information about anobject existing in the external environment by using light reflected orscattered from the external environment.

The scanning device 120 may include a light source 122 outputting aplurality of light beams having different characteristics and a hologramrecording medium 120 which scans the external environment by outputtinglight that has specific steering information and that interferes withthe light output from the light source 122.

The light source 122 may output the plurality of lights having differentcharacteristics. The characteristic may include at least one of awavelength and a phase. In an exemplary embodiment, the light source 122may output a plurality of lights having different wavelengths or aplurality of lights having different phases. In another exemplaryembodiment, the light source 122 may output a plurality of lights havingdifferent wavelengths and phases.

The light source 122 may include a laser diode generating light havinghigh coherence, but is not limited thereto. Since light having somedegree of spatial coherence may be sufficiently diffracted and modulatedby the hologram recording medium 124, any other light source may be usedas long as it emits light having some degree of spatial coherence.

The light source 122 may include sub light sources providing lighthaving different characteristics. In an exemplary embodiment, the lightsource 122 may include a first sub light source providing light having afirst wavelength and a second sub light source providing light having asecond wavelength different from the first wavelength.

In another exemplary embodiment, the light source 122 may include awavelength tunable laser providing light of different wavelengths. Thewavelength tunable laser may have a narrow line width and a widewavelength tuning range. In an exemplary embodiment, the line width maybe 100 kHz and the wavelength tuning range may be about 50 to about 80nm. Accordingly, a single wavelength tunable laser may output a largenumber of different wavelengths. The wavelength tunable laser may outputlight of different wavelengths in response to an electrical signalapplied thereto. A wavelength band may be about 600 to about 1500 nm.The wavelength tuning may be continuous or discontinuous. Alternatively,the light source 122 may also include a phase modulator providing lightof different phases.

Light having different steering information may be recorded on thehologram recording medium 124 via a hologram method. Of the recordedlight, light responsive to a characteristic of incident light may beoutput. For convenience of explanation, a incident on the hologramrecording medium 124 may be referred to as reference light, and lightoutput from the hologram recording medium 124 may be referred to assignal light.

The hologram recording medium 124 may include a material on which aplurality of signal light beams Ls may be recorded. In an exemplaryembodiment, the material may be a non-volatile material. A greaternumber of the signal light beams Ls may be recorded on the hologramrecording medium 124 according to an increase in the thickness thereof.The thickness of the hologram recording medium 124 may refer to a sizeof the hologram recording medium 124 in a direction parallel to a normalline of a surface on which the light output from the light source 122 isincident.

The hologram recording medium 124 on which the signal light Ls may berecorded may include various materials, for example, non-linear crystalssuch as LiNbO3, Photo-Thermo-Refractive (PTR) glass, and organic polymermaterials called photopolymers. A dynamic range may be used to determinethe capacity of the various materials to record a hologram thereof. Thedynamic range may be defined as the number of holograms with adiffraction efficiency of 100% that may be redundantly recorded in acertain thickness of the material. The dynamic range may be increasedproportionally to a refractive index size at which maximum modulationper unit thickness is possible. Since the dynamic range of LiNbO3crystal material is 1 to 2 (cm−1), and one or two signal light beams Lsmay be recorded on the LiNbO3 crystal material having a thickness ofabout 1 mm, it is not indicated to use the LiNbO3 crystal material forthe beam steering device 10 according to an exemplary embodiment. Thesignal light Ls may also be recorded on the PTR glass. However, sinceone signal light beam Ls may be recorded on the PTR glass materialhaving a thickness of about 1 mm, it may be desirable to increase thethickness of the PTR glass to record a large number of signal lightbeams Ls.

The hologram recording medium 124 according to an exemplary embodimentmay include a material including at least one of photo-polymer andinorganic crystal. The thickness of the hologram recording medium 124may be about 1 mm to about 10 mm. In an exemplary embodiment, about 190signal light beams may be recorded on a photo-polymer material having athickness of about 1 mm as reference light having a bandwidth of about0.26 nm, about 500 signal light beams may be recorded on photo-polymermaterial having a thickness of about 3 mm as reference light having abandwidth of about 0.1 nm, and about 500 signal light beams may berecorded on photo-polymer having a thickness of about 5 mm as referencelight having a bandwidth of about 0.05 nm.

Each of the signal light beams Ls recorded on the hologram recordingmedium 124 may include specific steering information. In an exemplaryembodiment, the steering information may include information about atleast one of an output direction and a divergence angle of the signallight beam. Thus, the signal light output from the hologram recordingmedium 124 may include its own steering information. In an exemplaryembodiment, a first signal light beam Ls having first steeringinformation including a first output direction and a first divergingangle may be output in the first output direction and at the firstdiverging angle. Further, each of the signal light beams Ls may have aunique characteristic, for example, a wavelength, a phase, or amodulation characteristic.

The signal light beams Ls may be recorded on the hologram recordingmedium 124 by a reference light in a holographic method and may beoutputted from the hologram recording medium 124 by a light having thesame characteristic as the reference light. In an exemplary embodiment,when the first signal light Ls, having the first steering information,and first reference light, having the first characteristic, are incidenton the hologram recording medium 124, the first signal light Ls may berecorded on the hologram recording medium 124 in a holographic method ofrecording interference patterns of the first signal light and the firstreference light. The holographic method may include any one of atransmission method, a reflection method, and a floating method. Then,when light, having the same characteristic as the first reference light,is incident on the hologram recording medium 124, only the first signallight beam Ls is output from among the signal light beams recorded onthe hologram recording medium 124. The first signal light Ls, thatreacts only with light having the first characteristic, is be output,but is not output when light having a second characteristic, differentfrom the first characteristic, is incident on the hologram recordingmedium.

Thus, the beam steering device 10 according to an exemplary embodimentmay scan the external environment by making light, having differentcharacteristics, incident on the hologram recording medium 124 and bythereby outputting signal light having different steering information.As described above, when the external environment is scanned using thehologram recording medium 124, it is not necessary to provide a separatemechanical device for adjusting an output direction of the light or thelike.

The processing device 140 may acquire information about an object in theexternal environment using the signal light Ls output from the scanningdevice 120. The processing device 140 may include a light receiver 142receiving the signal light Ls output from the scanning device 120 andscattered or reflected by an object and a processor 144 acquiringinformation about the object based on a result received from the lightreceiver 142.

The light receiver 142 may include a light detector outputting anelectric signal corresponding to the light received, for example, acurrent, a current-to-voltage conversion circuit converting the currentoutput from the light detector into a voltage, and an amplifieramplifying amplitude of the voltage, etc. In addition, the lightreceiver 142 may further include a lens condensing the light reflectedfrom the object and a filter filtering an electric signal of a specificfrequency, for example, a high pass filter, etc.

The light detector may be a light receiving device. In an exemplaryembodiment, the light detector may include an Avalanche Photo Diode(APD) or a Single Photon Avalanche Diode (SPAD). The light receiver 142may have the specific circuit configuration of an Analog Front End(AFE), a Time Digital Counter (TDC), etc. according to which of an APDand a SPAD is included in the light receiver 142. Such a specificcircuit configuration may be a general technology, and thus a detaileddescription thereof will be omitted.

The processor 144 may obtain information about the object based on theelectrical signal received from the light receiver 142. The processor144 may obtain the information about the object by detecting the peak ofthe electrical signal. In an exemplary embodiment, the processor 144 maydetect the peak by detecting a width of the electrical signal in ananalog manner. Alternatively, the processor 144 may detect the peak byconverting the electrical signal into a digital signal and thendetecting rising and falling edges of the digital signal. Alternatively,the processor 144 may detect the peak using a Constant FractionDiscriminator (CFD) method of dividing the electric signal into aplurality of signals, inverting and time-delaying some of the electricsignals, combining the inverted and delayed electric signals with theremaining signals, and detecting a zero cross point. The processor 144may further include a comparator to output the detected peak as a pulsesignal.

The processor 144 may determine whether an object is present based onwhether the peak is detected. Then, the processor 144 may determine aposition of the object by determining the signal light corresponding tothe light of which the peak is detected. In an exemplary embodiment, thesignal light may be identified by a modulation characteristic of thelight of which the peak is detected. The processor 144 may specifysteering information of the signal light from the characteristic of thedetected light based on a lookup table matching the characteristic andthe steering information and may determine the position of the objectusing the steering information of the specified signal light. Inaddition, the processor 144 may determine distance information regardingthe object, that is, depth information of the object, based on adetection time of the detected peak and an output time of the signallight output from the scanning device 120. A distance measuring methodusing the peak is a common technique, and thus a detailed descriptionthereof will be omitted.

The hologram recording medium 124 according to an exemplary embodimentmay output signal light (hereinafter, referred to as ‘wide range signallight’) having a divergence angle greater than a reference angle and mayalso output signal light (hereinafter, referred to as ‘narrow rangesignal light’) having a divergence angle less than the reference angle.The reference angle may be defined by a designer.

Since wide range signal light has a large divergence angle, the externalenvironment of a wide range may be scanned with the wide range signallight. In an exemplary embodiment, the wide range signal light may beused to determine whether an object is present or to identify a targetregion within the external environment within which the object ispresent. Since narrow range signal light has a small divergence angle, apartial region of the external environment, for example, the targetregion, may be scanned with the narrow range signal light. The narrowrange signal light may be used to obtain more precise information of theobject, for example, distance information regarding the object. Also,the number of the narrow range signal light beams may be greater thanthat of the wide range signal light. In an exemplary embodiment, widerange signal light and narrow range signal light may be allocated suchthat about 50 narrow range signal light beams are output in a regionwithin which one wide range signal light beam is output.

FIGS. 2A and 2B are reference diagrams for explaining wide range signallight according to an exemplary embodiment. Referring to FIG. 2A, widerange signal light Lbs having a convergence angle θc1, greater than areference angle, may be recorded on the hologram recording medium 124using reference light Lbr. The wide range signal light Lbs may beirradiated while the reference light Lbr is irradiated onto the hologramrecording medium 124. Then, an interference pattern between thereference light Lbr and the wide range signal light Lbs may be recorded,and thus the wide range signal light Lbs may be recorded on the hologramrecording medium 124.

As shown in FIG. 2B, when light Lbr,’ having the same characteristic asthe reference light Lbr, is irradiated onto the hologram recordingmedium 124 on which the wide range signal light Lbs has been recorded,the wide range signal light Lbs recorded with the interference patternmay be output from the hologram recording medium 124. A divergence angleθd1 of the output wide range signal light Lbs may be the same as theconvergence angle θc1 with which the wide range signal light Lbs wasrecorded. An output direction d1′ of the output wide range signal lightLbs may be the same as an incidence direction d1 with which the widerange signal light Lbs was recorded. In this way, wide range signallight Lbs, that reacts with only the light Lbr′ having the samecharacteristic as the reference light Lbr with which the wide rangesignal light Lbs was recorded, may be output but may not be output withrespect to light having a different characteristic. Therefore, steeringinformation of the wide range signal light Lbs output from the hologramrecording medium 124 may be specified as the incidence direction d1 andthe convergence angle θc1 of the wide range signal light Lbs incident onthe hologram recording medium 124, and the wide range signal light Lbsmay be output only by a light having a specific characteristic.

FIG. 3 is a reference diagram for explaining a method of scanning theexternal environment using wide range signal light according to anexemplary embodiment. A plurality of wide range signal light beams,having different steering information, may be recorded on the hologramrecording medium 124 shown in FIG. 3. When a plurality of referencelight beams having different characteristics are irradiated onto thehologram recording medium 124 of FIG. 3, wide range signal light beamsthat respectively react with the reference light beams, from among theplurality of wide range signal light beams may be diffracted and output.When the plurality of reference light beams having differentcharacteristics are sequentially incident onto the hologram recordingmedium 124 one by one, the plurality of wide range signal light beamsthat respectively reacts with the reference light beams may besequentially output one by one. Each of the plurality of wide rangesignal light beams may have different steering information and may beoutput in an output direction and at a divergence angle corresponding tothe steering information.

In an exemplary embodiment, when the first reference light beam Lbr isincident on the hologram recording medium 124, a first wide range signallight beam Lbs1, recorded by forming an interference pattern togetherwith the first reference light beam Lbr, may be output in the firstoutput direction d11 and at the first divergence angle θd11. When asecond reference light beam Lbr1, having a different characteristic fromthat of the first reference light beam Lbr1, is incident on the hologramrecording medium 124, a second wide range signal light beam Lbs2,recorded by forming an interference pattern together with the secondreference light beam Lbr1, may be output in the second output directiond12 and at the second divergence angle θd12. The second output directiond12 may be different from the first output direction d11. The firstdivergence angle θd11 and the second divergence angle θd12 may be thesame or different, whereas both the first divergence angle θd11 and thesecond divergence angle θd12 may be greater than a reference angle.

In an exemplary embodiment, when an external environment of 180 degreesin a forward direction is scanned using wide range signal light, thehologram recording medium 124 may output 6 wide range signal lightbeams, each having an angle of 30 degrees in an output direction of theneighboring wide range signal light beams and having a divergence angleof 30 degrees or more, and thus the external environment may be scanned.The number of the wide range signal light beams and the steeringinformation may be determined according to an application.

FIGS. 4A and 4B are reference drawings for explaining narrow rangesignal light Lfs according to an exemplary embodiment. Referring to FIG.4A, the narrow range signal light Lfs having a convergence angle θc2,less than a reference angle, may be recorded on the hologram recordingmedium 124 using the reference light Lfr. A first narrow range signallight beam Lfs may be incident on the hologram recording medium 124 in astate in which the reference light Lfr is irradiated onto the hologramrecording medium. Then, the narrow range signal light beam Lfs may berecorded on the hologram recording medium 124 by recording aninterference pattern of the reference light beams Lfr and the narrowrange signal light beams Lfs.

As shown in FIG. 4B, when light Lfr′ having the same characteristic asthe reference light Lfr with which the narrow range signal light Lfs wasrecorded on the hologram recording medium 124 is incident on thehologram recording medium 124, the narrow range signal light beam Lfs,recorded in the interference pattern, is be output from the hologramrecording medium 124. A divergence angle θd2 of the output narrow rangesignal light Lfs may be the same as a convergence angle θc2 with whichwhen the narrow range signal light Lfs was recorded. An output directiond2′ of the output narrow range signal light Lfs may be the same as theincidence direction d2 with which the narrow range signal light Lfs wasrecorded. The narrow range signal light Lfs that reacts only with lighthaving the same characteristic as the reference light Lfr with which thesignal light Lfs was recorded may be output but may not be output withrespect to light having a different characteristic from the referencelight Lfr. Therefore, steering information of the narrow range signallight Lfs output from the hologram recording medium 124 may be specifiedas the incidence direction d2 and the convergence angle θc2 of thenarrow range signal light Lfs incident on the hologram recording medium124, and the narrow range signal light Lfs may be output only by lighthaving a specific characteristic.

FIG. 5 is a reference diagram for explaining a method of scanning anexternal environment using a plurality of narrow range signal lightbeams Lfs according to an exemplary embodiment. The plurality of narrowrange signal light beams having different steering information may berecorded on the hologram recording medium 124 shown in FIG. 5. When aplurality of reference light beams having different characteristics areirradiated to the hologram recording medium 124 of FIG. 5, the narrowrange signal light Lfs that respectively reacts with each referencelight among the plurality of narrow range signal light beams Lfs may bediffracted and output. When the plurality of reference light beamshaving different characteristics are sequentially incident on thehologram recording medium 124 one by one, the plurality of narrow rangesignal light beams Lfs that respectively react with the reference lightbeams may be sequentially output one by one. Each of the plurality ofnarrow range signal light beams Lfs may have different steeringinformation, and may be output in an output direction and a divergenceangle corresponding to the steering information. In an exemplaryembodiment, when an n-th reference light beam Lfr1 is incident on thehologram recording medium 124, a first narrow range signal light beamLfs1, recorded by forming an interference pattern together with the n-threference light beams Lfr1, may be output in an n-th output directiond21 and an n-th divergence angle θd21. When an n+1th reference lightbeams Lfr2, having a different characteristic from the n-th referencelight beams Lfr1, is incident on the hologram recording medium 124, asecond narrow range signal light beams Lfs2, recorded by forming aninterference pattern together with the +1th reference light beam Lfr2,may be output in an n+1th output direction d22 and an n+1th divergenceangle θd22. The n+1th output direction d22 may be different from the nthoutput direction d21. The n-th divergence angle θd21 and the n+1thdivergence angle θd22 may be the same or different, whereas both then-th divergence angle θd21 and the n+1th divergence angle θd22 may begreater than a reference angle.

In an exemplary embodiment, the hologram recording medium 124 may output300 narrow range signal light beams, each having an angle of 0.1 degreeswith respect to an output direction between the neighboring narrow rangesignal light beams and a divergence angle θd of 0.1 degrees or more, andthus an external environment of about 30 degrees in a forward directionmay be scanned. The number of the narrow range signal light beams andsteering information may be determined adjusted as desired.

FIG. 6A is a diagram for explaining a relationship between referencelight and signal light according to an exemplary embodiment. FIG. 6B isa diagram illustrating an example in which signal light scans anexternal environment according to an exemplary embodiment. A pluralityof wide range signal light beams and a plurality of narrow range signallight beams may be recorded on the hologram recording medium 124. Thewide range signal light beams and the narrow range signal light beamsmay be output to be recorded by reference light having a differentwavelength. In an exemplary embodiment, the wide range signal lightbeams may be recorded and output by reference light of a firstwavelength band, and the narrow range signal light beams may be recordedand output by a reference beams of a second wavelength band. The widerange signal light beams may be classified into first to fifth widerange signal light beams according to an output region, and the narrowrange signal light beams may be allocated to output regions of the widerange signal light beams and classified into first to fifth narrow rangesignal light groups.

Even though the wide range signal light beams and the narrow rangesignal light beams have different ranges of a divergence angle andoutput direction, the wide range signal light beams and the narrow rangesignal light beams may be recorded together on the hologram recordingmedium 124 and may be output by reference light having a differentcharacteristic. Thus, the wide range signal light beams and the narrowrange signal light beams may be easily output.

Also, an external environment may be scanned more efficiently by usingthe wide range signal light beams and the narrow range signal lightbeams together. FIG. 7 is a flowchart for explaining a method ofscanning an external environment using signal light according to anotherexemplary embodiment. Referring to FIG. 7, the scanning device 120 mayextensively scan the external environment using the wide range signallight Lbs (S710). The light source 122 may output a plurality ofreference light beams having different wavelengths. The hologramrecording medium 124 may output a plurality of wide range signal lightbeams having different steering information that reacts with thewavelengths of the plurality of reference light beams. When theplurality of reference light beams having different wavelengths outputfrom the light source 122 are sequentially incident on the hologramrecording medium 124 one by one, the hologram recording medium 124 maysequentially output a plurality of wide range signal light beams havingdifferent steering information. The plurality of wide range signal lightbeams may be sequentially output in a specific direction. In anexemplary embodiment, when the reference light beams are sequentiallyoutput by the light source 122 in a direction with a large wavelength,the hologram recording medium 124 may sequentially output first throughfifth wide range signal light beams such that the output direction dchanges clockwise.

The processing device 140 may determine a target region in which anobject exists in the external environment using the wide range signallight Lbs (S720). The processing device 140 may detect a light scatteredor reflected by the object among the plurality of wide range signallight beams output as unique steering information and determine a targetregion of the external environment by using a peak of an electricalsignal corresponding to the detected light. In an exemplary embodiment,the processor 144 may determine a wide range signal light correspondingto an electrical signal of which a number of peaks is equal to orgreater than a reference number, and also determine the target regionusing steering information of the determined wide range signal light. Inan exemplary embodiment, when the obtained number of peaks from anelectrical signal corresponding to light reflected in a fourth region inFIG. 6B is equal to or greater than the reference number, the processor144 may determine the fourth region as the target region.

The scanning device 120 may scan the target region using a narrow rangesignal light (S730). In an exemplary embodiment, when it is determinedthat the fourth region of FIG. 6B is the target region, the processor144 may control the light source 122 to output the narrow range signallight to the target region. The light source 122 may cause a referencelight having a wavelength that reacts with the narrow range signal lightthat may be output to the target region to be incident on the hologramrecording medium 124. The hologram recording medium 124 may output afourth narrow range signal light Lfs that reacts with a light incidentfrom the light source 122.

The processing device 140 may acquire information about the object basedon the narrow range signal light Lfs (S740). The processor 144 maydetermine a position of the object by determining a narrow range signallight corresponding to the detected peak, and may also determinedistance information about the object, i.e., depth information of theobject, based on a detection time of the peak and an output time of thenarrow range signal light output from the scanning device 120.

Even though the wide range signal light and the narrow range signallight have different divergence angles and output directions, the widerange signal light and the narrow range signal light may be recordedtogether on the same hologram recording medium 124 and may be output byreference light having different characteristics. Also, the wide rangesignal light beams and the narrow range signal light beams may be easilyoutput and a structure of the scanning device 120 may be simple.Further, not all narrow range signal light beams may be output and onlya narrow range signal light beam corresponding to the target region inwhich the object exists may be output. Thus, the external environmentmay be scanned more efficiently.

A hologram recording medium or a plurality of hologram recording mediamay be used according to an exemplary embodiment. FIGS. 8A and 8B arediagrams showing a scanning device 120 b including a plurality ofhologram recording media 810, 820, and 830. As shown in FIG. 8A, theplurality of hologram recording media 810, 820, and 830 may be disposedto be in contact with each other. Alternatively, as shown in FIG. 8B,the plurality of recording media 810, 820, and 830 may be spaced apartfrom one other. Alternatively, although not shown in the figure, some ofthe plurality of recording media 810, 820, and 830 may be arranged to incontact with one other and the others may be spaced apart from eachother. The operation principle of the plurality of hologram recordingmedia 810, 820, and 830 may be the same as described above.

It should be understood that exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exemplaryembodiment should typically be considered as available for other similarfeatures or aspects in other exemplary embodiments.

While one or more exemplary embodiments have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope as defined by thefollowing claims.

What is claimed is:
 1. A beam steering method comprising: making firstreference light, having a first characteristic, incident on a hologramrecording medium on which signal light is holographically recorded,wherein the signal light comprises first signal light having firststeering information and recorded using the first reference light andsecond signal light having second steering information, different fromthe first steering information and recorded using a second referencelight, wherein the making the first reference light incident on thehologram recording medium causes outputting the first signal light to anexternal environment; and obtaining information about an object existingin the external environment using the output first signal light, whereinthe hologram recording medium is configured to output at least one of: afirst signal light group comprising a plurality of first signal lightbeams having divergence angles greater than a reference angle, and asecond signal light group comprising a plurality of second signal lightbeams having divergence angles less than the reference angle.
 2. Thebeam steering method of claim 1, further comprising: making the secondreference light, having a second characteristic different from the firstcharacteristic, incident on the hologram recording medium, therebyoutputting the second signal light wherein the information about theobject is obtained using the output first signal light and the outputsecond signal light.
 3. The beam steering method of claim 2, wherein thefirst characteristic and the second characteristic each comprise atleast one of a wavelength and a phase of light.
 4. The beam steeringmethod of claim 1, wherein the first steering information and the secondsteering information each comprise at least one of an output directionand a divergence angle.
 5. The beam steering method of claim 1, whereinthe information about the object comprises at least one of an absence ora presence of the object, a position of the object, and distanceinformation about the object.
 6. The beam steering method of claim 1,wherein the outputting the first signal light group comprises scanningthe external environment by outputting the plurality of first signallight beams included in the first signal light group in different outputdirections.
 7. The beam steering method of claim 1, wherein theoutputting the first signal light group comprises sequentiallyoutputting, one by one, the plurality of first signal light beamsincluded in the first signal light group.
 8. The beam steering method ofclaim 1, wherein the obtaining of the information about the objectcomprises determining a target region in the external environment withinwhich the object exists using the output first signal light group. 9.The beam steering method of claim 8, wherein the outputting the secondsignal light group comprises scanning the target region by outputtingthe plurality of second signal light beams included in the second signallight group in different output directions.
 10. The beam steering methodof claim 9, further comprising obtaining distance information about theobject using the output second signal light group.
 11. A beam steeringdevice comprising: a light source configured to output reference lightcomprising first reference light having a first characteristic andsecond reference light having a second characteristic, different fromthe first characteristic; and a hologram recording medium on whichsignal light is holographically recorded, wherein the signal lightcomprises first signal light having first steering information andrecoded using the first reference light and second signal light havingsecond steering information and recorded using the second referencelight; a processor configured to obtain information about an objectexisting in an external environment based on the signal light; whereinthe hologram recording medium is configured to scan the externalenvironment by outputting at least the first signal light having thefirst steering information when the first reference light is madeincident on the hologram recording medium, wherein the hologramrecording medium is configured to output at least one of: a first signallight group comprising a plurality of first signal light beams havingdivergence angles greater than a reference angle, and a second signallight group comprising a plurality of second signal light beams havingdivergence angles less than the reference angle.
 12. The beam steeringdevice of claim 11, wherein the hologram recording medium is furtherconfigured to output the second signal light having the second steeringinformation when the second reference light is made incident on thehologram recording medium.
 13. The beam steering device of claim 11,wherein the first characteristic and the second characteristic eachcomprise at least one of a wavelength and a phase of light.
 14. The beamsteering device of claim 11, wherein the first steering information andthe second steering information each comprise at least one of an outputdirection and a divergence angle.
 15. The beam steering device of claim11, wherein the information about the object comprises at least one ofan absence or a presence of the object, a position of the object, anddistance information about the object.
 16. The beam steering device ofclaim 11, wherein the hologram recording medium is configured to outputthe plurality of first signal light beams in different outputdirections.
 17. The beam steering device of claim 11, wherein theprocessor is configured to determine a target region in the externalenvironment in which the object exists using the first signal lightgroup and to obtain distance information about the object based on thesecond signal light group.
 18. A beam steering method comprising:providing a hologram recording medium on which signal light is recorded,wherein the signal light comprises at least a broad signal light beamhaving a divergence angle greater than a reference angle and at least afirst narrow signal light beam and a second narrow signal light beameach having a divergence angle less than the reference angle; makingfirst reference light, having a first characteristic, incident on thehologram recording medium, thereby causing the hologram recording mediumto output the broad signal light beam; obtaining primary informationabout an object using the broad signal light beam; making secondreference light, having a second characteristic different from the firstcharacteristic, incident on the hologram recording medium, therebycausing the hologram recording medium to output at least one of thefirst narrow signal light beam and the second narrow signal light beam;and obtaining secondary information about the object using the at leastone of the first narrow signal light beam and the second narrow signallight beam.